Prof Neville Pillay

Over the past five years, my research programme has focussed on the biology of southern African rodents. There is a paucity of information on southern African rodents, yet there is anecdotal evidence that several taxa are pests and some taxa have undetermined conservation status.

As an animal behaviourist, I have studied rodents to facilitate understanding of principles in animal behaviour. The study of animal behaviour (ethology) has its roots in comparative psychology but also deals with issues in ecology and evolution. My research has been multi-disciplinary in that my recent research can be regarded as psychobiology, integrating psychological, developmental and behavioural principles. In addition, I have used the comparative approach to understand the ecological, evolutionary and behavioural of some rodents, particularly the striped mouse Rhabdomys pumilio. The comparative approach has enhanced the understanding of the behavioural and evolutionary biology of this taxon.
Some of my students have worked on non-rodent taxa, including the feeding behaviour of elephants, the behaviour of free-living humpback dolphins, and foraging behaviour of captive baboons.

Overall, my research falls into three themes: 1) behaviour and speciation of southern African rodents; 2) reproduction, behaviour and life-history biology of small mammals; and 3) the welfare and management of captive animals.

• Behaviour and speciation of southern African rodents
  The aim here is to establish the level of interfertility between populations and/or chromosomal races of striped mice Rhabdomys pumilio. I have attempted to relate patterns of interfertility with genetic patterns. Collaborators (Rambau and Robinson, University of Stellenbosch) reported that there are 2 mtDNA clades of striped mice, one arid and the other mesic, and interestingly my results match those of the mtDNA patterns. Studies of behaviour and speciation of distantly-located populations are rare, perhaps because of assumed divergence in allopatry. Yet, such knowledge is essential for the striped mouse which has an isolation by distance population genetic structure, and comprises chromosomal variants and populations inhabiting vastly contrasting habitats. I have attempted to identify relationships between all these phenomena and speciation and to comment on the potential for gene flow between populations.
  
  I completed two studies on reproductive isolation in three distantly-situated striped mice populations, two of which had the same chromosomal number of 2n = 48 and the other 2n=46; the latter is the result of a Robertsonian fusion. These populations were located more than 900km apart from one another in different parts of South Africa. Regardless of chromosomal type, these populations were behaviourally incompatible, as a result of female preference of same-population over different-population mates and high levels of aggression in different population breeding pairs. There was no evidence of post-mating breakdown in those interpopulation pairs that did breed, confirming the predictions made by collaborators (Rambau and Robinson) that the chromosomal differences are insufficient to cause hybrid failure. However, recent work by Jenny Lancaster (MSc) and myself on the 46 and 48 races which occur only 50km apart on the highveld indicated behavioural compatibility and hybrid failure. Another study (in prep) suggests that behavioural fences (i.e. same sex behavioural breakdown) occur between striped mice populations. Ongoing studies include: the relationship between mate signal divergence and mtDNA differences and the relationship between behavioural compatibility and geographic distance. I am also searching for a contact zone between the two chromosomal forms.
  
  
• Reproduction, behaviour and life-history biology of small mammals
  The aim of the theme is to understand how environmental factors shape the biology of murid rodents. I have resolved the difficulties of separating phylogenetic from environmental influences by using either closely-related species (Otomyinae) or populations from different habitats (striped mice). In my initial work on striped mice, I perfected the fostering technique which, apart from revealing how adult behaviour is shaped by early influence, has been an invaluable tool for testing a range of hypotheses. Some major sub-themes are listed below.
  
  Incest/inbreeding. Projects include the behavioural mechanisms of kin recognition and the relationship between inbreeding occurrence and ecological circumstances. Several southern African rodent taxa have been used as models, particularly those in small, isolated populations. Current studies examine generational effects of inbreeding.
  
  Life history biology. These studies have been largely based on the postnatal growth and development in several rodent taxa to understand ecological determinants of life history patterns. Both common and rare species have been studied. In recent studies, manipulations of parental environment have been done to understand whether and how life history patterns change across generations. 2 PhD students, Tracy Aenmey and Jenny Lancaster, are continuing their studies on environmental effects on the sociality and population dynamics of rodents respectively. Both studies attempt to experimentally differentiate among the various factors influencing behaviour and life history traits rather than simply providing a description of these phenomena.
  
  Paternal care. This is a new development initiated by Carsten Schradin (postdoctoral fellow) and myself. Our first publication in 2003 presented the results of exhaustive field and laboratory studies which show that striped mice from two populations, one from the semi-arid desert and the other from moist grasslands, display highly-developed paternal care. The striped mouse is the only African murid that displays paternal care, and ours is the first study to provide evidence of paternal care in free-living rodents. Examples of other completed studies include sociality in different habitats, social flexibility, hormonal control of paternal care, and fitness consequences of paternal care.
  
  Foraging and social behaviour of ice rats. 2 PhD students, Andrea Hinze and Ute Schwaibold, have completed their experimental work on respectively the social behaviour and foraging ecology of ice rats (Otomys sloggetti robertsi) and both are writing up their theses in the form of a collection of papers. These studies tested the general hypothesis that the biology of the ice rats, particularly their foraging, burrowing and sociality, contributed to the large scale soil erosion in their alpine habitats in Lesotho. The ice rat is the only member of the Otomyinae which is confined to alpine habitats, and interesting comparisons can be made with its congeners occurring at lower, warmer altitudes (e.g. vlei rats) and relatives in the deserts (e.g. whistling rats). In one recent study, Ute and I showed that the gut of ice rats (compared to other otomyine rodents) has a longer small intestine and other features that would improve energy uptake in cold environments. A novel finding was that the gut length of females was longer in summer than in winter but the gut of males was unaffected. We concluded that the increase in gut length in females may be an adaptation for meeting the energy demands of pregnancy and lactation, indicating phenotypic plasticity in response to the poor quality vegetation and shorter growing season in alpine habitats.
  
  
• The welfare and management of captive animals
  My students and I have been studying the phenomenon of stereotypic behaviour and the application of environmental enrichment to address issues in animal welfare. Using the fostering technique, Ute Schwaibold and I showed that stereotypic behaviour is genetically transmitted in the striped mouse. In a recent study, Megan Jones and I reported that captive hamadryas baboons will work for food even if food is freely available or the animal is satiated, suggesting that foraging behaviour is inherently rewarding and that there is a behavioural need to forage. We suggest that the redirected foraging behaviour could be exploited as a form of environmental enrichment. Ongoing studies include fitness consequences of stereotypy, mechanisms and ontogeny of stereotypy, and the mechanisms underlying social foraging in captive primates.

Teaching:

• First year: Animal diversity
• Second year: Biotic diversity, Reproductive Biology
• Third year: Animal behaviour
• Honours: Behavioural and Evolutionary Ecology

Links

• Striped mouse project - Goegap Nature Reserve
• Photographs

1. Pillay, N. 2000. Reproductive isolation in three populations of the striped mouse Rhabdomys pumilio (Rodentia, Muridae): interpopulation breeding studies. Mammalia 64: 461-470.
2. Pillay, N. 2000. Female mate preference and reproductive isolation in populations of the striped mouse Rhabdomys pumilio. Behaviour 137: 1431-1441.
3. Pillay, N. 2000. Fostering in the African striped mouse: implications for kin recognition and dominance. Acta Theriologica 45:193-200.
4. Pillay, N. 2001. Reproduction and postnatal development in the bush Karoo rat Otomys unisulcatus (Muridae, Otomyinae). Journal of Zoology, London 254: 515-520.
5. Pillay, N. 2002. Reproduction and postnatal development in Littledale's whistling rat Parotomys littledalei (Muridae, Otomyinae). Mammalia 66: 71-82.
6. Bennett, LN & Pillay, N. 2001. Responses of male Rhabdomys pumilio to urine of conspecific females in different reproductive states. Proceedings of the 8th International Symposium on African Small Mammal, Paris, July 1999. IRD Éditions. Institut de Recherche pour le dévelopment - collection Colloques et séminaries. Pp.321-330.
7. Pillay, N. 2002. Inbreeding in Littledale's whistling rat Parotomys littledalei. Journal of Experimental Zoology 293: 171-178.
8. Pillay, N. 2002. Father-daughter recognition and inbreeding avoidance in the striped mouse, Rhabdomys pumilio. Mammalian Biology 67: 212-218.
9. Pillay, N. 2003. Reproductive biology of a rare African rodent, the water rat Dasymys incomtus. Journal of Mammalogy 84: 505-512.
10. Pillay, N., Alexander, G.J. & Lazenby, S.L. 2003. Responses of striped mice, Rhabdomys pumilio, to faeces of a predatory snake. Behaviour 140: 125-135.
11. Schradin, C & Pillay, N. 2003. Paternal care in the social and diurnal striped mouse (Rhabdomys pumilio): laboratory and field evidence. Journal of Comparative Psychology 117: 317-324.
12. Schwaibold, U. & Pillay, N. 2003. The gut morphology of the African ice rat, Otomys sloggetti robersti, shows adaptations to cold environments and sex-specific seasonal variation. Journal of Comparative Physiology (B) 173: 653-659.
13. Schradin, C & Pillay, N. 2004. The striped mouse from the succulent Karoo, South Africa: a territorial group living solitary forager with communal breeding and helpers at the nest. Journal of Comparative Psychology 118: 37-47.
14. Schradin, C. & Pillay, N. 2004. Prolactin levels in paternal striped mouse (Rhabdomys pumilio) fathers. Physiology and Behaviour 81: 43-50.
15. Schradin, C & Pillay, N. 2004. Demography of the striped mouse (Rhabdomys pumilio) in the succulent karoo. Mammalian Biology. In press
16. Schradin, C & Pillay, N. 2005. Intraspecific variation in the spatial and social organization of the African striped mouse. Journal of Mammalogy. In press
17. Schradin, C & Pillay, N. 2005. The influence of the father on offspring development in the striped mouse. Behavioural Ecology. In press
18. Schwaibold, U. & Pillay, N. 2001. Stereotypic behaviour is genetically transmitted in the African striped mouse, Rhabdomys pumilio. Applied Animal Behaviour Science 74: 273-280.
19. Jones, M. & Pillay, N. 2004. Foraging in captive hamadryas baboons: implications for enrichment. Applied Animal Behaviour Science. 88: 101-110. Key words: Rodents/ Animal behaviour/ Evolution/ Ecology/ Life history biology/ Ethology/Applied animal behaviour
20. Mullin, S.K., Pillay, N. & Taylor, P.J. 2001. Non-geographic variation in Dasymys incomtus (Rodentia: Muridae) in southern Africa. Durban Museum Novitates 26: 38-44.
21. Mullin, S.K., Pillay, N., Taylor, P.J. & Campbell, G. 2002. Genetic and morphometric variation in populations of South African Dasymys incomtus incomtus (Rodentia, Murinae). Mammalia 66: 381-404
22. Atkins S., Pillay, N. & Peddemors, VM. 2004. Spatial distribution of Indo-Pacific humpback dolphins (Sousa chinensis) at Richards Bay, South Africa: environmental influences and behavioural patterns. Aquatic Mammals 30 (1): 84-93.
23. Mullin, S.K., Pillay, N. & Taylor, P.J. 2004. Cranial variation and Geographic Patterns within the Dasymys rufulus complex (Rodentia: Muridae). Journal of Mammalogy. In press
24. Mullin, S.K., Pillay, N. & Taylor, P.J. 2004. Skull size and shape of Dasymys (Rodentia: Muridae) from sub-Saharan Africa. Mammalia. In press

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